Flaxseed is one of the major crops in Western Canada, Northern United States, South America and some European countries. Conventionally, flaxseed is processed into oil and the meal is used as an animal feed. Recently, flaxseed has become of increased importance in the Western diet as it contains a number of nutrients that are highly beneficial to human health. These include flaxseed oil (42–46%) which has high levels of linolenic fatty acid (55–59%), dietary fibre (24–28%) and lignans (0.5–1%), plus proteins (22–25%) and other minor components (Carter 1993, Potential of Flaxseed and Flaxseed Oil in Baked Goods and Other Products in Human-Nutrition. Cereal Foods World, 38(10):753–9; and Cui 1998, Flaxseed: a functional food for the 21st century. Canadian Chemical News, May Issue). Linolenic fatty acid is the essential fatty acid which can reduce the risk of heart disease (Cunnane et al. 1995, Nutritional attributes of traditional flaxseed in healthy young adults. Am J. Clin. Nutr. 61(1):62–68). Dietary fibre can control the levels of blood glucose and glycernic response (Cui 1998; Wood and Beer 1998, Functional oat products. In Functional Foods: Biochemistry & Processing Aspects. Technomic Publishing Company, Inc. Lancaster, Pa. Pp1–37). Evidence has shown that flaxseed and its extracts containing high levels of lignans and its hydrolysate, secoisolariciresinol diglycoside (SDG), can prevent and slow the growth of cancer cells (Thompson et al. 1996, Flaxseed and its lignan and oil components reduce mammary tumor growth at a late stage of carcinogenesis. Carcinogenesis, 17(6):1373–1376).
All these beneficial properties exhibited by flaxseed have stimulated numerous research papers and patents for extracting the useful components from flaxseed and its applications in food and pharmaceuticals. Prior processes are disclosed in Canadian Patent No. 2,167,951 (Cui and Mazza) which issued on Apr. 30, 2002 and Canadian Patent Application No. 2,304,303 (Myllymaki), filed on Mar. 31, 2000. This patent and patent application disclose laboratory scale methods that include a dehulling process for flaxseed. These laboratory scale methods are small scale, batch type dehulling processes for separating flaxseed into hulls and kernels and the subsequent extraction of useful components from the fractionated products. These processes are useful for small batches of less than 100 g per batch but are not useful for commercial scale processing of flaxseed.
Other prior documents disclose techniques for the extraction, isolation, and purification of lignans from flaxseed meal and its constituent component SDG. An example of such techniques is disclosed in U.S. Pat. No. 5,705,618 (Westcott et al.). Further documents disclose the application of lignans and SDG for improving human health (Thompson et al., 1996; Thompson 1998, Experimental studies on lignans and cancer. Baillieri's Clinical Endocrinology and Metabolism 12(4): 691–705; U.S. Pat. No. 5,846,944 to Prasad; and U.S. Pat. No. 5,837,256 to Clark et al.).
The desirable components of the flaxseed are distributed in different locations in flaxseed. For example, lignans and gums are found only in the hulls while most of the proteins and oils are in the kernel (Cui and Mazza, Canadian Patent No. 2,167,951). Therefore, the dehulling process provides an efficient method for a comprehensive utilization of flaxseed at the maximum potential and adds values to the crop. Without the dehulling process, the extraction of lignans from flaxseed meal is much less efficient and more complex, and it is not suitable for commercial production.
The prior processes disclosed in these documents are not suitable for commercial scale production of flaxseed and the commercial extraction of its components. For example, the dehulling process of flaxseed described in the above-mentioned documents are small scale batch type processes which can only process less than 100 grams of flaxseed per batch. At this scale, the commercial production of flaxseed components is not economically feasible.
Further, the extraction of lignans from the hull fraction as shown in these prior art processes is inefficient. Such extractions do not extract all of the available lignan. Much of it is left in the hull fractions and therefore wasted. Conventional extraction processes for hull fractions used in the art involve initial extraction of oil with hexane, followed by lignan extraction with alcohol, and gum extraction using water, leaving a residue of protein and insoluble fibre. This prior art sequence of extractions does not give rise to a lignan-rich fraction from flaxseed hull. There is therefore a need for a process for producing a lignan-rich component which extracts or uses substantially all of the lignan in the hull fraction of the flaxseed. See, for example, the publication of Nesbitt et al., 1999. Human metabolism of mammalian lignan precursors in raw and processed flaxseed. Am. J. Clin Nutr. 69:549–55.
Most animals are not tolerant of whole flaxseed and/or are unable to break down flaxseed to any significant extent within the intestinal tract. In order for such animals to derive benefit from flaxseed components, it would be beneficial to provide a process that could separate flaxseed components prior to including such components into feed.
Therefore, there is a need for a large scale process suitable for commercial production of flaxseed and for the production of nutraceutical products. There is also a need for a commercial production process which is economical.